I am writing a film script for a movie set in the trenches of France in the first world war. The project is still in early stages and I am throwing ideas about until I can pull something coherent out of it all. I would like to know if there were independent, almost mercenary or opportunistic groups taking advantage of the chaos, without particular loyalty to either side? Were there such things as sharp shooters or rifle skirmishers or proto-snipers? What was the maximum deadly range of the best rifle available during the war? Any help would be very welcome!